1. SWBAT analyze statements in if-then form.
SWBAT write converse, inverse, and contrapositives.
Splash Screen

2. conditional statement contrapositive
if-then statement
hypothesis
conclusion
related conditionals
converse
inverse
logically equivalent
Vocabulary

3. Concept

4. A. Identify the hypothesis and conclusion of the following statement.
If a polygon has 6 sides, then it is a hexagon.
If a polygon has 6 sides, then it is a hexagon.
hypothesis
conclusion
Answer: Hypothesis: A polygon has 6 sides. Conclusion: It is a hexagon.
Example 1

5. B. Identify the hypothesis and conclusion of the following statement.
Tamika will advance to the next level of play if she completes the maze in her computer game.
Answer: Hypothesis: Tamika completes the maze in her computer game. Conclusion: She will advance to the next level of play.
Example 1

6. B. Which of the choices correctly identifies the hypothesis and conclusion of the given conditional? To find the distance between two points, you can use the Distance Formula.
A. Hypothesis: You want to find the distance between 2 points. Conclusion: You can use the Distance Formula.
B. Hypothesis: You are taking geometry. Conclusion: You learned the Distance Formula.
C. Hypothesis: You used the Distance Formula. Conclusion: You found the distance between 2 points.
D. none of the above
Example 1

7. Measured distance is positive.
Write a Conditional in If-Then Form
A. Identify the hypothesis and conclusion of the following statement. Then write the statement in the if-then form.
Measured distance is positive.
Answer: Hypothesis: A distance is measured. Conclusion: It is positive. If a distance is measured, then it is positive.
Example 2

8. A five-sided polygon is a pentagon.
Write a Conditional in If-Then Form
B. Identify the hypothesis and conclusion of the following statement. Then write the statement in the if-then form.
A five-sided polygon is a pentagon.
Answer: Hypothesis: A polygon has five sides. Conclusion: It is a pentagon. If a polygon has five sides, then it is a pentagon.
Example 2

9. 2 and 7 are whole numbers, but –5 is an integer, not a whole number.
Truth Values of Conditionals
A. Determine the truth value of the conditional statement. If true, explain your reasoning. If false, give a counterexample.
If you subtract a whole number from another whole number, the result is also a whole number.
Counterexample: 2 – 7 = –5
2 and 7 are whole numbers, but –5 is an integer, not a whole number.
The conclusion is false.
Answer: Since you can find a counterexample, the conditional statement is false.
Example 3

10. If last month was February, then this month is March.
Truth Values of Conditionals
B. Determine the truth value of the conditional statement. If true, explain your reasoning. If false, give a counterexample.
If last month was February, then this month is March.
When the hypothesis is true, the conclusion is also true, since March is the month that follows February.
Answer: So, the conditional statement is true.
Example 3

11. When a rectangle has an obtuse angle, it is a parallelogram.
Truth Values of Conditionals
C. Determine the truth value of the conditional statement. If true, explain your reasoning. If false, give a counterexample.
When a rectangle has an obtuse angle, it is a parallelogram.
The hypothesis is false, since a rectangle can never have an obtuse angle. A conditional with a false hypothesis is always true.
Answer: So, the conditional statement is true.
Example 3

12. Concept

13. Concept

14. Bats are not birds, they are mammals.
Related Conditionals
Bats are not birds, they are mammals.
Bats have modified
hands and arms
that serve as wings.
They are the only
mammals that can fly.
NATURE Write the converse, inverse, and contrapositive of the following true statement. Determine the truth value of each statement. If a statement is false, give a counterexample.
Bats are animals that can fly.
Example 4

15. Conditional: First, rewrite the conditional in if-then form.
Related Conditionals
Conditional: First, rewrite the conditional in if-then form.
If an animal is a bat, then it can fly.
This statement is true.
Converse: If an animal can fly, then it is a bat.
Counterexample: A bird is an animal that can fly, but it is not a bat.
The converse is false.
Example 4

16. Inverse: If an animal is not a bat, then it cannot fly.
Related Conditionals
Inverse: If an animal is not a bat, then it cannot fly.
Counterexample: A bird is not a bat, but it is an animal that can fly.
The inverse is false.
Contrapositive: If an animal cannot fly, then it is not a bat.
The converse is true.
Example 4

17. Both the conditional and contrapositive are true. 
Related Conditionals
Check Check to see that logically equivalent statements have the same truth value.
Both the conditional and contrapositive are true. 
Both the converse and inverse are false. 
Example 4

18. A. All 4 statements are true.
Write the converse, inverse, and contrapositive of the statement The sum of the measures of two complementary angles is 90. Which of the following correctly describes the truth values of the four statements?
A. All 4 statements are true.
B. Only the conditional and contrapositive are true.
C. Only the converse and inverse are true.
D. All 4 statements are false.
Example 4

19. Homework
Page 111 #’s (even) 35-38, (even)